Simulating work in a tunnel after a quake, two slender robots with tiny heads attached with sensors walked through fake debris to extinguish a fire during a demonstration at the International Robot Exhibition in Tokyo.

The four-day event which kicked off today, is held once every two years in Japan's capital. This year it is drawing nearly 450 participating organisations - the biggest since it started about four decades ago. Some 57 of the groups come from countries including France, Britain, Russia and South Korea.

This year's show is focused on robotic equipment for disaster relief, assisting the elderly as well as their caregivers, and for farming. Disasters are a fact of life for Japan, an archipelago nation facing the 'Ring of Fire' - the rim of the Pacific Ocean that includes other earthquake and volcanic zones from Chile all the way around to New Zealand.

The two disaster-relief droids were developed in a project under the New Energy and Industrial Development (NEDO) – a national research organisation - that started after a devastating earthquake and tsunami hit northern Japan in 2011.

But unlike in Hollywood movies where bots can run, jump and fly at high-speeds, these droids are the slow and steady type. HRP-2 Kai and red-and-yellow coloured JAXON - named after the late singer Michael Jackson - were today focused on more serious tasks.

"HRP-2 Kai is now recognising debris and thinking with a sensor on its head about where to put its foot," said Fumio Kanehiro, researcher at the National Institute of Advanced Industrial Science and Technology that developed the robot.